Monitoring systems are utilized in a wide variety of mechanical and electrical applications, including industrial systems utilizing electrical devices for improved safety and security.
The subject addressable electric safety contact monitoring system may be used with many electrical devices including elevator door interlocks, gate switches, limit switches, escape hatches, emergency stop switches and devices using an electric contact point system. The device and method may be used for monitoring current crossing a set of contact points. A typical addressable electric safety contact monitoring system may include a mechanical or electromechanical latching device which engages a lock or similar receptor and which registers a condition of the device such as on-off, open-closed and locked-unlocked states. The addressable electric safety contact monitoring system is designed to ensure that a desired state is preserved, the location of the fault is located and to react when the desired condition no longer exists. Further, faults may be remotely observable for a large number of monitor locations.
An addressable electric safety contact monitoring system may have a useful application with the maintenance and operation of an elevator door interlock system, such as may be found in both modern and older buildings. In normal elevator operations, an elevator door interlock system will control the shaftway or hoistway doors at every floor, ensuring each is closed unless an elevator car is properly located at a given door and the appropriate mechanical or electrical signal is given so that the shaftway and car doors may open cooperatively. As is well known, elevator installations for large buildings will have a correspondingly large number of individual door interlock devices for every floor serviced by an elevator car in a given shaft. The number of such systems in a building is further multiplied by the number of elevator shafts installed therein. Such interlock devices are critically important for the safe operation of the elevator system and these all require periodic maintenance as well as occasional repair.
In a typical elevator installation, a door interlock system starts at either the top or bottom floor and an individual interlock device is installed at each successive floor. The devices utilize conventionally available electrical current, passing the current through each device and over a pair of electrical contact points when the interlock is properly engaged. Each working device passes the current to the next adjacent interlock location, usually the next floor above or below.
In a properly operating elevator installation, an operator may observe an all-closed condition whenever the current used at the originating location passes in series through every intermediate door interlock and signals an uninterrupted electrical circuit throughout the installed series of door interlocks. Typically such a signal, or lack thereof, can operate a safety relay switch at the elevator system control panel, shutting off the system power supply for safety as may be necessary. The current passes in series (rather than in parallel) as a safety measure to make sure that all installed door interlocks are operating properly before the elevator can function.
A significant, practical problem arises when there is a faulty door interlock, or an improperly engaged door interlock at an unknown location along the series of such door interlock devices in the elevator shaftway. Heretofore it has been necessary to send an elevator technician to each door interlock location to determine the source of such a fault.
An earlier method to monitor the state of doorkeepers in an elevator system is seen in the U.S. Pat. No. 6,382,362 which utilizes an optical interlock with a transmitter and receiver apparatus. Another example is seen in U.S. Pat. No. 6,988,594 which uses a temporal sensor for evaluating the status of a doorkeeper. These differ from the present monitoring system which offers another approach which is accurate, reliable and easy to troubleshoot. A further example of an elevator monitoring system is seen in U.S. Pat. No. 6,945,363 which discloses an electromagnetic beam detector system for monitoring the state of doors in a shaftway when the door locks are in a closed position. It is possible for such a system to provide a false positive result if a problem occurs or persists in the circuit itself, in which case a technician must visit each door to inspect the actual condition of its door interlock contact. The disclosures of each of the foregoing patents are hereby incorporated by reference.
The addressable electric safety contact monitoring system described in the present application also will be particularly useful for an elevator system and related components undergoing inspection or repairs.
Operation of the subject addressable electric safety contact monitoring system in, for example along a series of shaftway doors, may give a remote visible indication of safe, closed and locked locations, and a different remotely observable indication of the location where a fault occurs. Alternatively, the fault locations can be transmitted using an addressable mechanism that can be observed in a convenient location.
It is therefore an object of the present invention to provide an addressable electric safety contact monitoring system for remotely and visually monitoring a series of electric safety devices and the accompanying mechanical or electromechanical safety door interlocks to which they are related.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.